G'day Ray,
I find that I "guestimate" the time involved in a project. I am usually working on a number of things at once, so an accurate time is not possible, or more like I can't be bothered spending the time to time the time taken .
I have found over the years that there are a number of sticking price points eg $20, $50, $70, $100, $150 etc. That is if you can price under these, good, If you have to go above you may as well go quite a bit above. EG if someone is prepared to pay $50 they will in all likelihood not baulk at $65.
I use roughly $20 per hour, it's always an under estimate, as I don't factor in time taken to purchase timber, hardware or travel etc. Then I have a good look at the piece and decide the asking price. As JT has said, make notes of the prices you sell pieces for, because you can bet your life, if you take a punt as you can't remember what you sold it for previously it will come back to bight you on the behind.
The main thing is to ask yourself what you want out of the work, Enough to replace materials, buy a new tool every now and again and have a beer, or do want it to supplement your income?.